Jan Kara <jack@xxxxxxx> writes:
> From: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
>
> Generic per-cpu counter has some memory overhead but it is negligible for
> modern systems and embedded systems compile without quota support. And code
> reuse is a good thing. This patch should fix complain from preemptive kernels
> which was introduced by dde9588853b1bde.
>
> [Jan Kara: Fixed patch to work on 32-bit archs as well]
Ohh. Thanks for fixing that.
>
> Reported-by: Rafael J. Wysocki <rjw@xxxxxxx>
> Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> Dmitry, I have fixed the patch to use 'int' as quota stats used to instead
> of s64 you used. Now I plan to push it to Linus to fix the reported bug...
>
> fs/quota/dquot.c | 45 ++++++++++++---------------------------------
> include/linux/quota.h | 16 ++++------------
> 2 files changed, 16 insertions(+), 45 deletions(-)
>
> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> index 1ff9131..36e2af8 100644
> --- a/fs/quota/dquot.c
> +++ b/fs/quota/dquot.c
> @@ -228,10 +228,6 @@ static struct hlist_head *dquot_hash;
>
> struct dqstats dqstats;
> EXPORT_SYMBOL(dqstats);
> -#ifdef CONFIG_SMP
> -struct dqstats *dqstats_pcpu;
> -EXPORT_SYMBOL(dqstats_pcpu);
> -#endif
>
> static qsize_t inode_get_rsv_space(struct inode *inode);
> static void __dquot_initialize(struct inode *inode, int type);
> @@ -676,27 +672,10 @@ static void prune_dqcache(int count)
> }
> }
>
> -static int dqstats_read(unsigned int type)
> -{
> - int count = 0;
> -#ifdef CONFIG_SMP
> - int cpu;
> - for_each_possible_cpu(cpu)
> - count += per_cpu_ptr(dqstats_pcpu, cpu)->stat[type];
> - /* Statistics reading is racy, but absolute accuracy isn't required */
> - if (count < 0)
> - count = 0;
> -#else
> - count = dqstats.stat[type];
> -#endif
> - return count;
> -}
> -
> /*
> * This is called from kswapd when we think we need some
> * more memory
> */
> -
> static int shrink_dqcache_memory(int nr, gfp_t gfp_mask)
> {
> if (nr) {
> @@ -704,7 +683,8 @@ static int shrink_dqcache_memory(int nr, gfp_t gfp_mask)
> prune_dqcache(nr);
> spin_unlock(&dq_list_lock);
> }
> - return (dqstats_read(DQST_FREE_DQUOTS)/100) * sysctl_vfs_cache_pressure;
> + return (percpu_counter_read_positive(&dqstats.counter[DQST_FREE_DQUOTS])
> + /100) * sysctl_vfs_cache_pressure;
> }
>
> static struct shrinker dqcache_shrinker = {
> @@ -2497,11 +2477,11 @@ EXPORT_SYMBOL(dquot_quotactl_ops);
> static int do_proc_dqstats(struct ctl_table *table, int write,
> void __user *buffer, size_t *lenp, loff_t *ppos)
> {
> -#ifdef CONFIG_SMP
> - /* Update global table */
> unsigned int type = (int *)table->data - dqstats.stat;
> - dqstats.stat[type] = dqstats_read(type);
> -#endif
> +
> + /* Update global table */
> + dqstats.stat[type] =
> + percpu_counter_sum_positive(&dqstats.counter[type]);
> return proc_dointvec(table, write, buffer, lenp, ppos);
> }
>
> @@ -2594,7 +2574,7 @@ static ctl_table sys_table[] = {
>
> static int __init dquot_init(void)
> {
> - int i;
> + int i, ret;
> unsigned long nr_hash, order;
>
> printk(KERN_NOTICE "VFS: Disk quotas %s\n", __DQUOT_VERSION__);
> @@ -2612,12 +2592,11 @@ static int __init dquot_init(void)
> if (!dquot_hash)
> panic("Cannot create dquot hash table");
>
> -#ifdef CONFIG_SMP
> - dqstats_pcpu = alloc_percpu(struct dqstats);
> - if (!dqstats_pcpu)
> - panic("Cannot create dquot stats table");
> -#endif
> - memset(&dqstats, 0, sizeof(struct dqstats));
> + for (i = 0; i < _DQST_DQSTAT_LAST; i++) {
> + ret = percpu_counter_init(&dqstats.counter[i], 0);
> + if (ret)
> + panic("Cannot create dquot stat counters");
> + }
>
> /* Find power-of-two hlist_heads which can fit into allocation */
> nr_hash = (1UL << order) * PAGE_SIZE / sizeof(struct hlist_head);
> diff --git a/include/linux/quota.h b/include/linux/quota.h
> index 2789d07..94c1f03 100644
> --- a/include/linux/quota.h
> +++ b/include/linux/quota.h
> @@ -174,8 +174,7 @@ enum {
> #include <linux/rwsem.h>
> #include <linux/spinlock.h>
> #include <linux/wait.h>
> -#include <linux/percpu.h>
> -#include <linux/smp.h>
> +#include <linux/percpu_counter.h>
>
> #include <linux/dqblk_xfs.h>
> #include <linux/dqblk_v1.h>
> @@ -254,6 +253,7 @@ enum {
>
> struct dqstats {
> int stat[_DQST_DQSTAT_LAST];
> + struct percpu_counter counter[_DQST_DQSTAT_LAST];
> };
>
> extern struct dqstats *dqstats_pcpu;
> @@ -261,20 +261,12 @@ extern struct dqstats dqstats;
>
> static inline void dqstats_inc(unsigned int type)
> {
> -#ifdef CONFIG_SMP
> - per_cpu_ptr(dqstats_pcpu, smp_processor_id())->stat[type]++;
> -#else
> - dqstats.stat[type]++;
> -#endif
> + percpu_counter_inc(&dqstats.counter[type]);
> }
>
> static inline void dqstats_dec(unsigned int type)
> {
> -#ifdef CONFIG_SMP
> - per_cpu_ptr(dqstats_pcpu, smp_processor_id())->stat[type]--;
> -#else
> - dqstats.stat[type]--;
> -#endif
> + percpu_counter_dec(&dqstats.counter[type]);
> }
>
> #define DQ_MOD_B 0 /* dquot modified since read */
--
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